Illinois State Climatologist Office

Cold Start to the Year

Based on preliminary data, the average statewide temperature for January was 21.1 degrees, 3.7 degree below normal. The statewide average precipitation for January was 1.50 inches, 0.43 inches and 22 percent below normal. Here are the maps for January 2010: temperature departure and precipitation and snowfall totals.

Third Coldest Start to the New Year on Record

The statewide average temperature from January 1-12 was 9.5 degrees, 14.4 degrees below normal. This is the third coldest January 1-12 period on record in Illinois, based on preliminary data. Much colder-than-normal conditions have prevailed across Missouri, Iowa, Minnesota, and the High Plains states. Click on the map to the right for the January 1-12 temperature departures. Temperatures are expected to moderate somewhat for the second half of January, according to the NWS Climate Prediction Center.

One of the impacts of this stretch of cold weather has been ice jams on many rivers and streams across Illinois. Here are reports from the NWS for northern Illinois and central Illinois.

Unusually cold temperatures, sometimes accompanied by windy conditions, can be dangerous. The effects of windchill are discussed here. The state of Illinois has a web site www.keepwarm.illinois.gov with information on keeping warm this winter. Additional information about winter storms in Illinois can be found here.

Fourth Wettest Year on Record

Based on preliminary numbers, the annual precipitation for 2009 in Illinois was 50.27 inches, 11 inches above normal. This ranks as the fourth wettest year on record since statewide records began in 1895.

All four wettest years have been in the last 20 years of the record. The normal statewide annual precipitation in Illinois is 39.2 inches. The outstanding feature is the two back-to-back exceptionally wet years of 2008 and 2009. Together they account for 100.8 inches of precipitation. That is an extra 22.4 inches of precipitation over the two-year period.

As it now stands, the annual temperature for 2009 in Illinois was 51.2 degrees, 0.8 degrees below normal. The outstanding colder-than-normal months in 2009 were January, July, August, and October.

Cold, Wet December Finishes Out Cold, Wet Year

Based on preliminary data, the average statewide temperature for December in Illinois was 28.9 degrees, 1.0 degree below normal. The statewide average precipitation for December was 4.11 inches, 1.42 inches and 53 percent above normal. Here are the maps for December 2009: temperature departure and precipitation departure and snowfall totals.

Dreaming of a White Christmas? Odds Slim in Illinois

Based on historical reports of snow on the ground Christmas morning, people in northern Illinois have the highest odds of 30 to 50 percent. Naturally the odds decrease farther south but even southern Illinois sees one every once in a while. Your best place for having a white Christmas in Illinois? That would be Freeport in the northwest corner of the state at 56 percent.

The Christmas Day with the most snow on the ground in recorded history was 1951, according to long-term records. Aurora had an incredible 31 inches piled up that day from 12 days of nearly non-stop snow and temperatures below freezing... more on the 1951 Christmas and the odds of a white Christmas.

First Major Winter Storm of the Season Hits Midwest

The first major winter storm of the season struck the Midwest on December 8-9, 2009. A strong low-pressure system moved out of the southwestern US, into the central Plains states, across the Midwest and Great Lakes, and on into eastern Canada. This system produced impressive amounts of snow and high winds, leading to blizzard warnings in many locals. Cold, Arctic air moved in behind this system, causing temperatures that were 15 to 25 degrees below normal across Illinois on December 10... more on the 2009 blizzard.

Climate Events of 2009 in Illinois

Find the significant climate-related events of 2009 in Illinois here.

• Seventh Warmest November on Record
• Second Wettest October on Record
• Cool, Wet Growing Season Delays Harvest
• September Brings Uneven Rainfall across State
• Impacts of El Niño on Temperature and Precipitation
• Tracking the first fall freeze across the Midwest
• Illinois Agricultural Disaster Declaration
• Cool, wet summer
• New average wind speed maps
• Coldest July on record
• June - another wet month
• Hot, humid weather arrives
• Fifth Wettest Sprint on Record
• Sixth Wettest April on Record
• March - Wet in the North, Dry in the South
• Where is Spring
• Average Last Spring Frost
• February - More Rain, Less Snow
• Illinois Temperature Roller Coaster
• Former Champaign-Urbana weather observer passes away
• Cold January
• Arctic Air Grips Illinois

Climate Events in Illinois Archive

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